A new bestseller, The 17-Day Diet: A Simple Plan That Targets Both Belly Fat and Visceral Fat and Produces Fast Results That Last! by Mike Moreno, MD, brims with the charming bedside manner you wish your doctor had. But is the plan a prescription for healthy weight loss or just the latest gimmick?

The Program: For the first 17 days, you eat all you want from Dr. Moreno's approved low-and no-carb foods list. For the next 17, you alternate these low-carb days with days allowing a few carbohydrates like beans and sweet potatoes before 2 PM. This is Dr. Moreno's version of alternate-day fasting, the practice of restricting your calories every other day. (A few studies suggest this aids weight loss, but even the author of those studies thinks there's not enough research to draw conclusions from.) The third 17-day interval introduces portion control and a few treats, like low-fat desserts. If at the end of this cycle you aren't at your goal weight, you start over with the cycle of your choice.

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The Claim: Dr. Moreno believes that changing the diet every 17 days keeps your metabolism in a state of "confusion," speeding up weight loss, targeting belly fat, and letting you avoid the normal plateaus. Dr. Moreno suggests you can expect to lose up to 12 pounds in the first 17 days alone. He claims this combination of alternate-day fasting and a strict limit on starch and sugar turns the body into a fat-burning machine.